Internally insulated vessel-bottom



Sept. 5, 1967 j` T HORTON ET AL 3,339,779

INTERNALLY INSULATED VE-SSEIrBOTTOM Filed Sept. 29, 1964 A fr0/m5 ys.

United States Patent O This invention relates to storage vessels. More particularly, this invention is concerned with large insulated storage Vessels.

Insulated vessels are used for storing a wide variety of liquids including materials which are liquid at ambient temperatures and pressures as well as materials which are liquid at increased pressures and/or lowered temperatures. Some of the liquids stored at low teniperatures are liquied gases such as ammonia, carbon dioxide, methane, ethane and propane.

The vessels used for storing such liquids are generally large and are iield erected from prefabricated materials. While the insulation can be placed on the outside it is advisable in many installations and for particular service to internally insulate the vessel.

Internally insulated vessels broadly comprise a closed outer shell, an inner shell inside the outer shell in spaced relationship thereto and insulation material between the inner and outer shells. Such vessels commonly have substantially flat inner and outer bottom sheets and cylindrical vertical side walls. A roof generally is joined to the outer side wall. This roof can have suspended internal insulation or an internal roof sheet can be joined to the inner side wall and insulation positioned between the inner and outer roofs.

Storing low temperature liquids in such vessels, whether internally or externally insulated, leads to dimensional changes of the inner bottom sheet `because of differential contraction. This can create large radial loads, the presence of which are likely to be at least troublesome by causing joint failure and leaks and even severe enough to cause failure of the vessel under service conditions.

There is accordingly provided'by the subject invention a novel insulated vessel in which the inner -bottom sheet is provided with expansion means, such as in the form of a loop, to facilitate expansion and contraction of the bottom sheet and minimize the `creation of radial loads. More particularly, there is provided an inner bottom sheet having the outer edge thereof fixed in lposition and expansion means which permits the remainder of the bottom sheet to contract and expand with teinperature changes. The invention will be further described in conjunction with the attached drawings in which:

FIGURE l is an elevational sectional View, partly broken away, of a vessel showing one embodiment of the expansion means; and i FIGURE 2 is similar to FIG. 1 but shows a second embodiment of the expansion means in the bottom.

In each of the drawings identical or substantially similar parts or elements are given the same number in thel different figures.

FIGURE 1 shows a vessel having an outer shell having bottom sheet 10 which rests on a suitable foundation or load bearing surface and side wall sheet 11 which joins the bottom sheet. A roof (not shown) is also provided and is joined to the top portion of side wall 11. Although the lower part of the vessel is shown partly sunk below the ground surface, the vessel bottom 10 can be placed at or above the ground surface.

The bottom 10 is generally circular and the side wall cylindrical. The outer shell, including the bottom, side Wall and roof can be made of any suitable material but una ICC

advisably is metal, such as low carbon steel or aluminum, although other materials such as reinforced plastics can be used.

The inner shell of the vessel has a bottom sheet 12 and a side wall sheet 13 which is generally a concentric cylinder with respect to outer side wall 11. An internal roof, not shown, can rest on the inner side wall with insulation placed between it and the outer roof. The lbottom 12 is approximately flat and is composed of a major Hat sheet 14 which can extend over almost the entire bottom area. At or near the Aperipheral area of bottom sheet 14 is provided expansion means, such as in the form of loop 15 having a vertical cross-section in the shape of an inverted U. The loop`15 circles around the periphery of the bottom thereby forming a raised annular rib of generally toroidal shape. The expansion loop 15 can be fabricated separately and then joined to the bottom sheet y14 or the loop can be formed as an integral part of plates or strips used in making the bottom. Y

As shown in FIG. l the loop 15 has an inner leg 22 joined to bottom 12 as by rounded transition corner 40 and outer leg 16 projecting below the bottom 14 and into an annular concrete retaining ring 17, such as of perlite which fixes or secures leg 16 in place. Between the outer circumferential edge of loop 15 and side wall 13 is spacer 18 which joins the loop 15 and wall 13 in a liquid impermeable manner. The lower edge 19 of inner side wall 13 can be secured to the concrete ring 17 and thus held in place against movement. The spacer 18 is advisably made of minimal width so that its dierential contraction and expansion during vessel temperature cycles will be insignificant.

Supporting the inner bottom sheet 14 is load bearing insulating material 20. The bottom sheet 14 is not bonded or joined to insulation 20 or concrete 17 and is free to move thereon through expansion and contraction with temperature changes.

Between the outer side wall 11 and inner side wall 13 is Iplaced suitable insulating material 21. The insulation 21 must withstand storage loads without appreciable deformation. Insulating plastic foams such as the polyurethane type can be used for this purpose. The side wall 13 can suitably be bonded to the insulation 21.

Any suitable materials can be used for the inner shell bottom and side wall as well as any inner roof which may be used. Thus, the inner shell can be made of steel, aluminum or a suitable plastic material, advisably reinforced with glass fibers.

When the empty vessel is brought from ambient temperature to a lower temperature by the introduction of a liqueed gas the bottom sheet 14 contracts upon being cooled. As this happens its shrinkage is accommodated by gradual lateral inward movement of inner leg 22 of the loop 1'5 with moderate deflection of the loop 15 and slidable movement of the sheet 14 on the supporting insulation. The loop 15 is relatively ilexible and yields easily with contraction or expansion of bottom sheet 1-4. Development of radial loads on the side wall 13 by differential temperature movement of the inner bottom is thus minimized or prevented and all joints are maintained liquid tight. Such structure gives exterior dimensional stability to the vessel by securing the outer edge of the bottom in place while permitting the remainder of the bottom to contract and expand with temperature changes.

The structure of FIG. 2 illustrates `a second embodiment of the invention. Those parts which are the same as in FIG. l have been numbered the saine. The bottom sheet 1-4 is joined to expansion loop 31 which is similar to loop 15 of FIG. 1 except that it, loop 31, has no outer leg 16. Inner leg 22 and outer leg 23 are alike and each can be joined to the bottom 14 and spacer 32 as by the rounded transition corner 40. Loop 31 is joined at the lower edges of its sides to bottom sheet 14 and to annular spacer plate 32 which constitutes a at rin-g between the loop 31 and outer side wall 11. The ring 32 is joined to both by suitable means, such as welding in the case of metal loops and side walls. The inner side wall 30 has its lower edge joined to the ring 32 in a leak-proof manner, such as by welding. The loop 31 functions in the same way as loop 15. Neither plate 32 nor bottom sheet 14 are bonded to the supporting insulation 20 and are free to move with temperature induced dimensional changes. However, the outer edge 50 of plate 32 is joined to side wall 11 and is thus fixed or secured in position against movement. Dimensional change in the inner bottom 14 due to temperature variation is accommodated by loop 31 without changing the position or dimensions of the `outer edge 50.

In the drawings the insulated walls are shown disproportionately thick compared with the internal capacity which would be many times greater in large `iield-erected storage vessels. The drawing proportions were used however to clearly illustrate the invention.

What is claimed is:

'1. A cylindrical insulated liquefied gas above-ground storage vessel comprising an outer metal shell and an inner metal shell with insulation between the shells, said inner shell having a circular essentially flat bottom sheet, `an essentially smooth side wall sheet joined to the bottom sheet, an annular metal expansion rib in the bottom sheet in the region of its periphery and parallelingly adjacent to, but slightly spaced from, the side wall sheet, and a ring-like metal sealing strip joining the outer wall of the expansion rib to the outer shell side wall, and

the bottom edge of the side wall sheet is joined to the sealing strip.

2. A cylindrical insulated liquefied gas above-ground storage vessel comprising an outer metal shell and an inner metal shell with insulation between the shells, said inner shell having a circular essentially iiat metal bottom sheet, an essentially smooth metal side wall sheet joined at essentially a right angle to the bottom sheet, and a raised annular metal expansion rib in the bottom sheet in the region of its periphery and parallelingly adjacent to, but slightly spaced from, the side wall sheet, the raised rib having an inverted U-shaped cross-section and the outer leg of the rib depends vertically below the bottom sheet and is anchored against lateral movement by restraining means below the rib and between the inner and outer metal shells.

3. A vessel according to claim 2 in which the lbottom includes a ring-like metal sealing strip joining the outer leg of the rib to the side wall sheet.

References Cited UNITED STATES PATENTS 882,678 3/ 1908 Harry 220--10 2,301,061 11/1942 Logeman 220-1-8 2,889,953 6/ 1959 Morrison. 3,088,621 5/ 1963 Brown. 3,092,933 6/1963 Closner et al. 220-18 3,150,794 9/ 1964 Schlumberger et al. 3,151,416 10/1964 Eakin et al 220-18 THERON E. CONDON, Primary Examiner.

JAMES R. GARRETT, Examiner. 

1. A CYLINDRICAL INSULATED LIQUEFIED GAS ABOVE-GROUND STORAGE VESSEL COMPRISING AN OUTER METAL SHELL AND AN INNER METAL SHELL WITH INSULATION BETWEEN THE SHELLS, SAID INNER SHELL HAVING A CIRCULAR ESSENTIALLY FLAT BOTTOM SHEET, AN ESSENTIALLY SMOOTH SIDE WALL SHEET JOINED TO THE BOTTOM SHEET, AN ANNULAR METAL EXPANSION RIB IN THE BOTTOM SHEET IN THE REGION OF ITS PERIPHERY AND PARALLELINGLY ADJACENT TO, BUT SLIGHTLY SPACED FROM, THE SIDE WALL SHEET, AND A RING-LIKE METAL SEALING STRIP JOINING THE OUTER WALL OF THE EXPANSION RIB TO THE OUTER SHEEL SIDE WALL, AND THE BOTTOM EDGE OF THE SIDE WALL SHEET IS JOINED TO THE SEALING STRIP. 